2001 Volume 50 Issue 1 Pages 30-33
Limitting current density ilim of oxygen reduction was measured under a thin NaCl solution film. The reciprocal value of the obtained ilim increased proportionally with an increase in the electrolyte layer thickness δ when the δ ranged from 20μm to 100μm. From the dependency of the ilim on the δ, the oxygen reduction mechanism under a thin electrolyte film was proposed. In the proposed model, the oxygen reduction consists of three consecutive processes; dissolution of oxygen into the electrolyte film from gas phase, diffusion through the electrolyte film and charge transfer at electrolyte/electrode interface. From the analysis on the basis of the model, the diffusion coefficients of oxygen in the electrolyte film were obtained to be 5.9×10-9 m2s-1 and 6.1×10-9 m2s-1 for 0.5kmol/m3 and 5.4kmol/m3 NaCl solution films, respectively, and the rate-determining rates of dissolution at gas/electrolyte interface were determined to be approximately 5Am-2 and 3Am-2 for 0.5kmol/m3 and 5.4kmol/m3 NaCl solutions, respectively.
